Steerable medical device

ABSTRACT

A steering device, such as for use in a guidewire for percutaneous transluminal insertion into the coronary vascular system is provided. The guidewire comprises an elongate flexible housing having proximal and distal ends and at least one lumen extending through the length of the housing. The guidewire has a steering element secured within the lumen and adapted to displace the distal end of the housing in a lateral direction. At least one deflection wire extends through the flexible housing extending from a distal point of attachment to the proximal end. Axial movement of the deflection wire displaces a distal steering region of the housing in a lateral direction.

BACKGROUND OF THE INVENTION

This is a continuation-in-part of application Ser. No. 583,819, filedSep. 17, 1990, now U.S. Pat. No. 5,108,368, inventors Julius G.Hammerslag and Gary R. Hammerslag, entitled "Steerable Medical Device";which is a continuation-in-part of application Ser. No. 461,049, filedJan. 4, 1990, now U.S. Pat. No. 4,998,916; which is acontinuation-in-part of application Ser. No. 295,124, filed Jan. 9,1989, now U.S. Pat. No. 4,921,482.

The present invention relates to steering devices such like. Moreparticularly, the present invention relates to catheters and guidewiresthat are steerable through body lumen or cavities and positionablewithin or aimable at obstructions, organs or tissue within the body froma position external to the body.

Medical catheters generally comprise elongate tube-like members whichmay be inserted into the body, either percutaneously or via a bodyorifice, for any of a wide variety of diagnostic and therapeuticpurposes. Such medical applications frequently require use of a catheterhaving the ability to negotiate twists and turns, particularly withregard to certain cardiovascular applications.

One such application, "Percutaneous Transluminal Coronary Angioplasty"(balloon angioplasty), requires manipulation of a catheter from aposition outside the patient's body through extended portions of thepatient's arterial system to the stenotic site for the purpose ofalleviating the obstruction by inflating a balloon. This particularprocedure has been performed with increasing frequency over the pastyears in preference to open heart bypass surgery, when possible.

In a typical angioplasty procedure, a guidewire is transluminallyinserted into the brachial or the femoral artery, to be positionedwithin the stenotic region and followed by a balloon catheter. Thecardiologist usually pre-bends the distal tip of the guidewire beforeinsertion and then rotates (or torques) the wire once it has reached abranch artery to enable the guidewire to enter the branch. If the angleof the bend has to be adjusted, the guidewire must be removed, re-bentand reinserted, sometimes several times. Particular difficulty isencountered with prebending where an artery branches at one angle, andthen sub-branches at a different angle. This procedure is attended bythe risk of significant trauma to the arterial lining, and, in manycases, the obstruction cannot be reached at all with the guidewire andcatheter.

Coronary arteries are tortuous, have many sub-branches and often theobstruction is either located where the diameter of the artery is smallor, by its very presence, the obstruction leaves only a very smallopening through which a guidewire and/or catheter can be passed.Consequently, the cardiologist often finds it very difficult to maneuverthe guidewire or catheter, which are typically several feet long, fromthe proximal end.

Steering the pre-bent guidewire is further complicated by the fact thatbranches project at all different radial angles, thus necessitatingrotation of the guidewire to the appropriate degree to enter the desiredarterial branch. However, rotation of the distal end of the wiretypically lags behind rotation of the proximal, control end, so thatprecise rotational control is not possible. Also, friction in thearteries can cause the distal end to rotate in a jerky fashion which cantraumatize the vascular intima.

In another application, Transluminal Laser Catheter Angioplasty (laserangioplasty), the delivery of laser energy from an external source to anintraluminal site to remove plaque or thrombus obstructions in vesselsis accomplished by providing a waveguide such as a fiber optic bundlewithin a catheter. The nature of laser angioplasty requires an evengreater ability to precisely manipulate the catheter, to control and aimthe laser light at the specific plaques or thrombi to be removed.

A variety of attempts have been made in the past to provide catheterswhich are steerable from the proximal end to enable the catheter to beaimed or advanced through non-linear body cavities. For example, U.S.Pat. No. 4,723,936 to Buchbinder, et al. discloses a balloon catheter,which is said to be steerable from the proximal end. The catheter isprovided with a deflection wire going along the entire length of thecatheter, which may be axially displaced to cause deflection. However,the tip of the catheter can be bent in one direction only, and theentire catheter must be rotated or torqued to be guided. A furtherdisadvantage of this device is the inability to effectively straightenthe catheter once it has been bent. Any ability of the Buchbindercatheter depends upon the axial compression of the steering wiretherein. In addition, the design requires a relatively large diameterdeflection wire, which precludes extremely thin diameter catheters, suchas those preferred for use for laser or balloon angioplastyapplications.

U.S. Pat. No. 3,470,876 to Barchilon discloses a catheter device havinga central lumen extending therethrough, and four tensioning cordsextending along an inner wall of the catheter. The '876 patentspecifically recites that catheters may be produced in accordance withthe Barchilon design having diameters of 0.125 to 2 inches, and aresuited for applications such as within the duodenal bulb or ascendingcolon. These diameters are unsuited for use as a guidewire in coronaryangioplasty, which typically requires diameters in the area of as smallas from about 0.014 to 0.018 inches.

In the context of coronary angioplasty applications, the prior artgenerally suffers from disadvantages such as limited steerability andexcessive external diameters. Limited catheter tip steerability resultsin greater time spent in the body and significantly elevated risk oftrauma both to the vascular intima and to the patient in general.Multiple insertions of guidewires or catheters may lead to thrombosis,as a result of coagulation commencing along a guidewire surface.Additionally, precise directional control in laser angioplasty is of theutmost importance to assure accurate aiming of the laser beam to ablatethe attendant plaque. However, the only prior art catheters havingmulti-directional steerability are typically greatly in excess ofpractical angioplasty catheter diameters.

In addition to limited steerability, the prior art guidewires, such asthose disclosed by Buchbinder and in U.S. Pat. No. 4,719,924 toCrittenden, rely upon the spring tension of the guidewire coil (and theresilience of the distal end of the deflection wire, in the case ofBuchbinder) to return the guidewire to the straight, unbent position.However, as important as deflecting the wire to enter a branch artery isstraightening the wire after the branch is negotiated. Any ability tostraighten in the prior art devices described above results from thespring tension or other structure in the distal end of the wire, whichstructures also compromise the desired floppiness of the guidewire tip.

Thus, there remains a need for a small diameter steering device, whichmay be readily adapted for use in the construction of either guidewiresor catheters, and which is especially suited for procedures such asballoon or laser angioplasty. Preferably, the steering device isconstructed in a manner which permits a diameter as small as that ofexisting dilatation catheters or guidewires used in angioplastyapplications. The steering device additionally permits controlledlateral deflection of the distal tip.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the present inventiona steerable device for insertion into a body cavity and controllednegotiation of branches and turns therein. The steerable devicecomprises an elongate flexible housing having a proximal end and adistal end and at least one lumen extending axially therethrough. Asteering element is secured within the lumen and adapted to displace thedistal end of the housing in a lateral direction.

At least one deflection wire is axially movably disposed within thelumen of the flexible housing, and extends from a distal point ofattachment with respect to the steering element, throughout the lengthof the flexible housing to the proximal end thereof. Axial movement ofthe deflection wire in a proximal direction cooperates with therelatively fixed functional length of the steering element to produce alateral force, thereby displacing the axis of a portion of the housingin a lateral direction.

Preferably, the proximal end of the functional region of the steeringelement is secured within the lumen to substantially prevent axialmotion with respect to the tubular body. In one embodiment, the steeringelement is secured within the lumen by soldering.

Preferably, the steerable device further comprises a wire guide foraxially slidably receiving the deflection wire, proximal to the point ofattachment between the deflection wire and the steering element. A wireguide can conveniently be secured to both the interior wall of theelongate tubular body, and to the proximal end of the steering element.

In a preferred embodiment, the steerable device further comprises ameans for transmitting rotational torque between the flexible housingand the deflection wire. The preferred torque transmitting means for useherein comprises complementary surface structures on the deflection wireand the interior of the tubular body, which permit axial reciprocalmotion of the deflection wire within the tubular body, but substantiallyprevent rotation of the deflection wire with respect to the tubularbody.

In accordance with a further aspect of the present invention, there isprovided a steerable implement comprising an elongate flexible housinghaving proximal and distal ends and a central lumen extendingtherebetween. A steering region on the distal end of the housing isflexible in a lateral direction. An axially extending steering elementis secured within the steering region of the housing and adapted todisplace the steering region of the housing in the lateral direction.

At least one deflection wire is provided, having proximal and distalends and extending along the housing. A distal portion of the wire issecured with respect to the steering element. A control is furtherprovided at the proximal end of the housing for engaging the proximalend of the deflection wire to enable the deflection wire to be displacedaxially in relation to the housing. The axis of at least a portion ofthe steering element is displaced laterally in response to axialdisplacement of the deflection wire, thereby causing the distal end ofthe housing to bend out of the line of the housing longitudinal axis.

Preferably, the steering element is secured with respect to the housingat a point within about 2 cm of the distal end of the housing to form afulcrum. The elongate flexible housing is relatively axiallynoncompressable on the proximal side of the fulcrum. The axiallynoncompressable portion of the housing preferably comprises solid walltubing and/or spring coil.

In a spring coil embodiment, the spring coil extends distally past thefulcrum and beyond the distal end of the steering element. The portionof the spring coil disposed distally of the fulcrum is loosely wound, sothat adjacent windings of spring coil are not normally in contact withone another.

Preferably, the fulcrum comprises a tubular wire guide which is securedboth to the interior of the elongate flexible housing, and to thesteering element. Preferably, at least one torque transmitter isprovided for transmitting rotation between the deflection wire and thetubular housing

In accordance with a further aspect of the present invention, there isprovided a torque transmitter for transmitting rotational torque betweenan elongate tubular guidewire or catheter housing and a core wireextending axially therethrough, said core wire of the type adapted foraxial reciprocal movement with respect to the housing. The torquetransmitter comprises a first torque transmitting surface on the corewire and a complementary second torque transmitting surface on thehousing, so that engagement of the first and second transmittingsurfaces transmits rotational movement between the core wire and thehousing.

Preferably, the first torque transmitting surface on the core wirecomprises a generally planer surface lying on an axis which is generallyparallel to the longitudinal axis of the core wire.

The second torque transmitting surface preferably comprises a region ofreduced interior cross-sectional area of the lumen extending through theelongate tubular housing.

In an alternate embodiment of the torque transmitter in accordance withthe present invention, the core wire is provided with a length ofrelatively flattened ribbon like torque transmission region. The torquetransmission ribbon area extends through the lumen in a torquetransmitter tube secured to the interior wall of the elongate housing.The lumen of the torque transmitter tube is provided with a noncircularinterior cross-sectional configuration, such as oval or other flattenedconfiguration to substantially prevent rotation of the ribbon within thetorque transmitter tube.

In accordance with a further aspect of the present invention, there isprovided a steerable device for percutaneous transluminal insertion intothe coronary or peripheral vascular systems, and controlled negotiationof branches and turns therein. The device comprises an elongate supportstructure having a proximal and a distal end for transmitting axialforce from the proximal end of the support structure to the distal endthereof. Transmission of axial force is accomplished principally by thenon axially collapsible properties of the elongate support structure.

A steering element extends distally from the distal end of the supportstructure, thereby providing a fulcrum at the intersection of thesupport structure and the steering element. A core wire extendsgenerally parallel to the support structure and is secured to thesteering element at a point of attachment which is distal from thefulcrum. Axial movement of the core wire in a proximal directionrelative to the support structure causes a lateral deflection of thesteering element.

Preferably, the tubular body extends distally beyond the fulcrum tosurround the steering element. Preferably, the fulcrum is disposedwithin about 10 mm from the distal end of the steerable device, and,more preferably, the fulcrum is disposed within about 6 mm from thedistal end of the steerable device.

Further features and advantages of the present invention will beapparent from the detailed description of preferred embodiments whichfollows, when considered together with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional perspective view of a steerable guidewireaccording to the present invention, with the outer tubular casingremoved.

FIG. 2 is an elevational sectional view of the guidewire of FIG. 1,illustrated in a first deflected position.

FIG. 3 is an elevational sectional view of the guidewire of FIG. 1,illustrated in a second deflected position.

FIG. 4 is a partial sectional perspective view of a steerable laserangioplasty catheter according to the present invention.

FIG. 5 is a further embodiment of the steerable guidewire of the presentinvention.

FIG. 6 is a schematic view of the guidewire of FIG. 1, illustrated asnegotiating an arterial branch point and approaching an arterialstenosis.

FIG. 7 is an elevational perspective view of a further embodiment of asteering device according to the present invention.

FIG. 8 is an elevational perspective view of still a further embodimentof the present invention.

FIG. 9 is a cross-sectional view along the line 9--9 of the device ofFIG. 8.

FIG. 10 is a simplified front elevational view of the device shown inFIG. 8, following application of an anchor cap.

FIG. 11 is a simplified front elevational view of the device shown inFIG. 7, following application of an anchor cap.

FIG. 12 is a partial sectional perspective view of a "ribbon" steeringdevice according to the present invention, with the outer tubular casingremoved.

FIG. 13 is an elevational perspective view of a another embodiment of a"ribbon" steering device according to the present invention.

FIG. 14 is a side-elevational view of a guidewire incorporating a singledeflection wire embodiment of the steering device in accordance with thepresent invention.

FIG. 15 is an enlargement of a distal portion of the guidewireillustrated in FIG. 14.

FIGS. 16, 17 and 18 show an enlarged view of the guidewire illustratedin FIG. 15.

FIG. 19 is a side-elevational view of the region marked 19 in FIG. 14.

FIG. 20 is an elevational cross-sectional view through the lines 20--20in FIG. 19.

FIG. 21 is an elevational cross-sectional view taken along the lines21--21 in FIG. 15.

FIG. 22 illustrates a helical channel in the distal end of a hypotubesegment, adapted to receive a spring coil.

FIG. 23 illustrates one embodiment of a central core wire or deflectionwire in accordance with one aspect of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, there is disclosed an elongate flexible implement10, having a tubular body 11 with a proximal end 12 and a distal end 14.The distal end 14 comprises a steering region 16, and the proximal end12 is provided with a control 18 for steering the implement 10, whichmay be, for example, a steerable guidewire or catheter. Although thesteering device of the present invention will generally be describedherein as incorporated into an angioplasty guidewire, it is to beunderstood that one skilled in the art will be able to readily adapt thesteering device to other medical and non-medical applications.

The body 11 of steerable implement 10 may be any desired length frominches to many feet depending upon the intended application. In anembodiment useful as an angioplasty guidewire or catheter, the body 11will typically be several feet long, and will preferably be about135-180 cm, as is typical of existing angioplasty catheters andguidewires respectively. However, any suitable length may be used.Typically, the proximal most 120 to 150 cm of the body 11 is hypotube,as is well known in the art, and the distal 30 cm comprises a metalcoil.

The body 11 may be constructed in any of a variety of ways known in theart, such as by tightly winding a coil of metal wire, or extrusion of arelatively flexible biocompatible polymer such as polyethylene. Woundguidewires preferably comprise a high tensile strength wire of aresilient, non-corrosive metal such as stainless steel or platinum, andmay have a circular cross section with a diameter of from about 0.001 to0.020 in. The wire may alternatively have a rectangular cross section offrom about 0.001 to 0.020 inches by from about 0.001 to 0.040 inches, orother variations known in the art. Construction materials and techniquesfor manufacturing wire wound guidewires are well known in the art, and atypical 180 cm teflon coated 0.014 inch or 0.016 inch diameternon-steerable guidewire may be obtained from U.S. Catheter, Inc., adivision of C. R. Bard, Inc., located in Billerica, Mass., U.S.A.

The external diameter of wire wound guidewires will of course be afunction of the intended application. The wire wound coronaryangioplasty guidewires incorporating the steering device of the presentinvention are preferably wound to have an external diameter in the rangeof from about 0.014 inches to about 0.018 inches. In steerable catheterapplications, the diameter of the catheter can be varied to optimize thediameter of a central working channel as desired, while stillmaintaining a sufficiently small exterior diameter for the intendedapplication. Steerable balloon angioplasty catheters incorporating thepresent invention will typically have an exterior diameter in the rangeof from about 0.020 inches to about 0.041 inches or larger as permittedby location of the lesion.

Preferably, the exterior surface of the wound coil type guidewire shaft10 is provided with an elastic, biocompatible coating or sheath toprovide a smooth outer surface. Suitable coatings can be formed bydipping, spraying or wrapping and heat curing operations as are known inthe art. Alternatively, heat shrinkable tubing can provide a suitableouter sheath. A coating material should be selected which will permitsufficient flexing of the body 11 without cracking, will minimizesliding friction of the implement 10 during insertion and removal, andis substantially chemically inert in the in vivo vascular environment. Avariety of suitable materials are known, including, for example,polytetrafluoroethylene, urethane or polyethylene.

The body 11 of flexible implement 10 typically terminates at its distalend 14 in a closed tip 20. Numerous guidewire and catheter tipconstructions are known in the art and need not be detailed extensivelyherein. Typically, the tip 20 is formed by a rounded braze or solderjoint, which may also serve to secure the distal ends of the deflectionwires. As a safety feature, to facilitate complete removal of fragmentsof a broken guidewire, the deflection wires can extend distally beyondtheir point of attachment to the ribbon or post, to function as a safetywire, or a separate safety wire may be secured at one end to the insideof the tip 20, and at the other end to the post 22 or support 24.Alternatively, the tip 20 is constructed of a resilient polymericmaterial such as silicone or urethane which will minimize trauma to thevascular intima, as will be appreciated by one of skill in the art.

Disposed intermediate the tip 20 and body of a flexible implement 10 inaccordance with the present invention is a floppy but controllablesteering region 16. Steering region 16 is constructed in a manner thatfacilitates lateral displacement of the tip 20 relative to the axis ofthe body 11, through physical design and/or choice of flexibleconstruction materials.

For example, in a typical angioplasty guidewire or catheter, where theflexible body 11 comprises a metal wire coil, the revolutions of wireper unit of axial distance along the body is reduced in the steeringregion 16 relative to body 11 to provide a looser wound coil havingspace 17 between adjacent wire loops, as illustrated in FIGS. 1-6. Thus,referring to FIG. 2, it can be seen that lateral deflection of steeringregion 16 to the left may involve both an axial compression of adjacentwire loops on the inside surface 36 of the bend, and an axial separationof the adjacent wire loops on the outside surface 38 of the bend.

Alternative designs or materials can be employed, provided that thecatheter exhibits sufficient lateral flexibility. In general, thesteering region 16 may be made from a variety of suitable metal orplastic coils or flexible sleeves. Materials opaque to X-rays, such asplatinum, gold, tungsten, tantalum or the like, may be advantageouslyincorporated therein, to act as a fluoroscopic marker to aid invisualization.

In accordance with the "post" embodiment of the steering mechanism ofthe present invention, a steering post 22 is provided, extending in agenerally axial direction within the steering region 16 of flexible body11. Preferably, the steering post 22 is disposed coaxially within thecentral lumen of steering region 16 when the steering region 16 and body11 are linearly aligned, such as when at rest. See FIG. 1. As will bedescribed, the steering post 22 is secured in the steering region 16 ina manner that substantially prevents axial displacement thereof yetpermits lateral deflection of the axis of the steering post 22 away fromthe axis of body 11.

Post 22 preferably comprises a resilient shaft which may be molded orextruded from any of a variety of materials, such as nylon, and may havea cross-sectional dimension of from about 0.002 inches up to about 0.012inches for use in a typical steerable angioplasty guidewire embodiment.Alternatively, a variety of resilient or springy metals in the form ofwire can also be used to form post 22, such as phosphor bronze, springsteel, Nitinol, or other resilient metal. In general, it is desirable toselect a material which will permit some degree of bending and return toits original shape, and will resist axial compression under the forcestypically applied in the intended use of the steerable implement 10.

The length of steering post 22 will, of course, be dependant upon thelength of the steering region 16. In a typical steerable guidewire forangioplasty applications, the entire steering region 16 will be on theorder of from about 0.040 to about 1.0 inches and preferably from about0.120 to about 0.150 inches long, and the steering post 22 may be fromone-quarter to two-thirds that length. Although steering post 22 mayextend distally all the way to the distal tip 20 of the steerableimplement 10, it is preferred to limit the length to the proximalone-half or one-third of the axial length of steering region 16 tominimize rigidity in the steering region 16 yet permit sufficientsteerability thereof.

For example, in a typical angioplasty guidewire the distal end 27 ofsteering post 22 will be spaced apart from the interior surface of tip20 by a distance of from about one-tenth to one-half an inch or more,thus permitting the steering region 16 of the catheter shaft to be asfloppy as desired. However, in an embodiment where the distal portion ofa fiber optics bundle or flexible tube for defining a working channeladditionally functions as the steering post 22, the post 22 will extendall the way to the distal tip 20 and be exposed to the outside by way ofan opening therethrough. See, for example, FIG. 4.

In a preferred embodiment, steering post 22 is further provided with abead or enlarged region 26 to optimize transmission of lateral forcefrom the steering post 22 to the wall of steering region 16. For thispurpose, bead 26 is most effectively located at or near the distal endof steering post 22. Bead 26 may be formed by dipping or coatingtechniques, or may be a preformed member having an opening therein forsliding over the end of steering post 22. Alternatively, post 22 can bemolded or milled to provide a bead 26 integrally formed thereon. Bead 26is preferably substantially circular in a cross section perpendicular tothe axis of post 22, and the external diameter of the bead 26 is onlyslightly less than the interior diameter of the steering region 16 sothat maximum lateral motion of the steering post 22 is transmitted tothe steering region 16, but bead 26 also remains only in slidablecontact with the interior surface thereof.

The proximal end 23 of the steering post 22 is mounted to or inpivotable contact with a radial support 24, in a manner which permitspivoting of the steering post 22 throughout a full 360° range of motionabout the axis of body 11. The post may also be molded or milled as anintegral part of disk 24. The support 24 comprises any means by whichthe deflection wires 28 are displaced radially outwardly from the axisof the tubular body 11, such as by the thickness of the post 22 or otherstructure including the plate embodiment illustrated in FIGS. 1-3.

Referring to FIG. 1, the support 24 of the illustrated embodimentcomprises a circular disk 25 located within the tubular body 11 of thesteerable implement 10, preferably located near the distal end thereof.The disk 25 is axially secured within the tubular body 11 to provide astationary radial support for at least one deflection wire 28, andpivotable mount for steering post 22. Disk 25 may be attached, forexample, by friction fit between adjacent turns of coiled spring wire.Steering post 22 preferably is attached to or in contact with the disk25 in a manner which permits it to swivel from 90 degrees to close to 0degrees, relative to the lateral plane of disk 25.

The disk 25 may be made of stainless steel or any of a variety of othersuitable materials such as other metals or plastic polymers which willprovide a sufficiently axially rigid seat for the proximal end 23 ofsteering post 22. Disk 25 may be formed by stamping from sheet stock anddrilling, injection molding, or other techniques well known in the art.Preferably, a central depression or orifice is provided thereon, forproviding an axial seat for steering post 22. The diameter of disk 25can vary, however, it will typically be no greater than, but mayapproximate the outside diameter of the steerable implement 10.Diameters from about 0.14 to 0.050 inches may preferably be used in theconstruction of cardiac angioplasty catheters.

Lateral deflection of the steering post 22 away from the axis of body 11is accomplished by proximal axial displacement of any of a plurality ofdeflection wires 28 extending proximally throughout the length offlexible body 11. Although only a single deflection wire 28 or twodeflection wires can be used, preferably three or four deflection wires28 are employed in the "post" embodiment to provide a full 360° range ofmotion of the steering region 16 about the axis of the body 11, as willbecome apparent. Only a single deflection wire 28 will be described indetail herein.

The distal end of deflection wire 28 is secured such as by adhesives (orbrazing or soldering, etc.) to the steering post 22 at the distal endthereof, or at a variety of other locations along the length of post 22.By "attached" or "secured" to the post and similar language herein, itis to be understood that the deflection wire 28 is mechanically linkedto the post 22 but need not necessarily be directly secured thereto. Forexample, the deflection wire 28 could be secured to an annular flange orring surrounding the post or other structure which may be convenientfrom a manufacturing standpoint to provide a sufficiently secure linkageto accomplish the intended steering function. Alternatively, an eye onthe end of the deflection wire can surround the post 22 and rest againsta stop formed by a milled shoulder or adhesive, or other means ofattachment as will be apparent to one of skill in the art.

In one embodiment, the deflection wire 28 preferably extends radiallyoutwardly from the point of attachment to the steering post 22 to thesupport 24. For this purpose, the support 24 is preferably provided witha notch or orifice 40 for each deflection wire 28 to extend through,said orifice 40 spaced radially outwardly from the axis of the tubularbody 11 by a first distance. The distal end of each deflection wire 28is secured to the steering post 22 at a point radially displaced fromthe axis of the steering post 22 by a second distance, and the firstdistance is preferably greater than the second distance to maximize thelateral component of force. The second distance preferably approacheszero; however, it will inherently include the radius of the steeringpost 22 where the deflection wire 28 is secured intermediate the twoends thereof.

In the preferred embodiment of the present invention, four deflectionwires 28 are provided, each passing through an orifice 40 in support 24spaced at angles of approximately 90° apart from each other along theplane of the support 24. In a three deflection wire embodiment, asillustrated in FIG. 1, each orifice 40 is separated from each adjacentorifice by an angle of approximately 120°.

The deflection wires may be made of stainless steel, nylon or any othersuitable material which provides sufficient tensile strength andflexibility. Preferably, the deflection wires are braided from multiplestrands, as is detailed below. The diameter of the wires can range from0.001 to 0.005 inches or more, and suitability of particular sizes ormaterials can be readily determined by experimentation.

A control device 18 for steering the catheter is shown schematically inFIGS. 1-3. The control device 18 is preferably provided at its centerwith a pivotable mount 32 to permit it to be tipped throughout a full360° range of motion. In the illustrated embodiment, control 18comprises a circular plate 34 secured to proximal end 12 of flexibleshaft 10 by way of pivotable mount 32. Deflection wires 28 are spacedequally radially outwardly from the pivotable center of the controldevice and at equal angular distances around the plate 34. Deflectingplate 34 from a plane normal to the axis of shaft 10 transmits force viaone or more deflection wires 28, a component of which is resolved into alateral force to deflect the catheter tip toward or away from thelongitudinal axis of catheter. Selective tipping of the deflection plate34 results in rotation of the catheter tip to any desired orientation.

A variety of alternative control devices can be envisioned for use withthe steerable implement of the present invention. For example, a "joystick" type device comprising a single lever which can be displaced toany position throughout a nearly hemispherical range of motion might beused. As a further alternative, a portion of the proximal end 12 oftubular body 11 is enlarged to a cross section of a half inch or largerto facilitate grip. The enlarged section is provided with a plurality ofaxially slidable switches, one corresponding to each deflection wire 28.Manipulation of the switches by the thumb or forefinger will obtain thedesired deflection of steering region 16. As will be appreciated by oneof skill in the art, any control device will preferably be provided witha stop to prevent bending of the post 22 or steering region 16 past itselastic limit.

A variety of factors impact the amount of the lateral force componentexerted on steering post 22 by axial, proximal displacement of any ofdeflection wires 28. For example, as orifice 40 is moved further in aradially outward direction, the lateral force component will increase.Lateral displacement of orifice 40, however, is constrained by themaximum diameter that the steerable implement can have for an intendedapplication.

Alternatively, shortening the axial distance from the support 24 to thepoint of attachment 42 of the deflection wire 28 to the steering post 22increases the angle between the axis of post 22 and deflection wire 28,thereby increasing the lateral component of force. For this reason,support 24 is typically within one or two inches, and preferably lessthan one inch, from the distal tip 20 of an angioplasty catheter orguidewire embodiment of the invention.

A further alternative is illustrated in FIG. 5. In this embodiment, afulcrum 44 is provided at a point intermediate the radial support 24 andpoint of attachment 42 for maintaining the deflection wire 28 concave ina radial inward direction. The fulcrum 44 may conveniently comprise asubstantially radially symmetrical member such as a sphere or toroid,which can also function to limit proximal axial movement of steeringpost 22 through a central opening in support 24. In this embodiment, thepoint of attachment of deflection wires 28 may be to the fulcrum 44instead of directly to the steering post 22.

In accordance with a further aspect of the present invention, there isprovided a steerable medical implement for use in percutaneoustransluminal laser angioplasty applications. Referring to FIG. 4, thereis disclosed an elongate flexible implement 45 comprising at its distalend a floppy steering region 46. As described with previous embodiments,enhanced flexibility may be imparted to steering region 46 by providingspacing 47 between adjacent loops of wound wire 48.

A radial support means 49 is disposed at the proximal end of steeringregion 46, which may comprise a circular plate 50 or other structure fordisplacing deflection wires 52 radially outwardly from the axis ofimplement 45.

A waveguide such as a fiber optic bundle 54 extends the entire length ofthe implement 45, for directing laser light from a source (notillustrated) disposed at the proximal end of the implement 45, to apoint of application within a coronary artery at the distal tip 56 ofthe implement 45. For this purpose, the optical pathway 54 extendsthroughout the length of steering region 46 and traverses tip 56 by wayof an opening 58 therein.

Each of the deflection wires 52 is secured at its distal end to thefiber optic bundle 54 at a point intermediate radial support 49 anddistal tip 56. Preferably, as has been previously described, the pointof attachment of deflection wires 52 to the fiber optic bundle 54 isless than half the distance and preferably is within one-third of thedistance between the radial support 49 and distal tip 56, in order tooptimize the lateral component of force.

Thus, utilizing a control device as previously described, a laserangioplasty catheter incorporating the present invention permits thecontrolled direction of a beam of light transmitted through fiber bundle54 at any desired point within a full 360° circle on a plane normal tothe axis of the implement 45.

As is well known in the fiber optics art, numerous functions can beaccomplished through a waveguide such as fiber bundle 54. For example,substantially parallel but discrete bundles of fiber optics can besecured adjacent one another within the fiber bundle 54 to permit aplurality of discrete light transmitting channels. Alternatively, aplurality of concentric optical pathways can be provided as is wellknown in the art.

A plurality of discrete optical pathways may advantageously be used toperform a variety of functions. For example, a first optical pathwaymight be utilized to permit visualization of the stenotic site or othersurface to be treated. A separate optical pathway may be utilized totransmit light for illuminating the site. Yet a third optical pathwaymight be utilized to transmit the laser light. These and other aspectsof the fiber optics and laser light source are well known to thoseskilled in the fiber optics art.

A variety of additional functions may be performed through use of theadditional interior space within the housing of steerable implement 45.For example, in a preferred embodiment, an aspiration duct may beprovided near the distal end of the implement 45, for suctioning debrisor gases which may be generated as a result of the action of the laser.Alternatively, in place of a waveguide 54, a flexible tube may beincorporated into the steering device of the present invention, therebyproviding a working channel to receive additional implementstherethrough.

Referring to FIG. 7, there is disclosed a further embodiment of thesteering device in accordance with the present invention. The steerabledevice illustrated in FIG. 7 can be incorporated into a guidewire, ordirectly into a catheter, such as a balloon dilation catheter, or otherelongate implement for which steerability is desired. It is to beunderstood that while certain preferred dimensions and constructionmaterials will be recited in the discussion of the present embodiment,these illustrate a single angioplasty guidewire embodiment only and inno way limit the scope of the present invention.

The steering device 60 preferably is incorporated into a steerableguidewire, of the type made from an elongate flexible hypotube andtubular spring coil 61 having a central lumen extending therethrough.The spring coil 61 may be further provided with an outer sheath orcoating, as are known in the art, or the spring coil may, by itself,serve as the outer wall of the guidewire. As is well known in the art,the proximal end of the spring coil 61 is made up of a plurality ofadjacent loops of wire, which may in turn be connected to a solid walledtube such as a length of hypodermic needle stock. Typically, a 150 cmlength of hypotube, having a nominal 0.0135 inch outside diameter and0.007 inch inside diameter will be used for this purpose.

Lateral flexibility of the spring coil 61 at a distal steering regioncan be enhanced by providing a spacing between adjacent loops of thespring coil. These features are illustrated in FIGS. 1-6 of a previousembodiment of the present invention, and need no further discussionhere. Alternatively, the adjacent loops of wire in the steering regioncan be in contact with one another, i.e., no axial spacing, when thesteering region is in an orientation co-linear with the axis of theadjacent guidewire.

Extending axially within the steering region of the spring coil 61 is acentral post 62. Post 62 is preferably made from a flexible polymericextrusion, or from a metal or metal alloy such as Nitinol, although anyof a wide variety of materials can be incorporated into the post 62 ofthe present invention. Most preferably, the post 62 comprises a nylonrod having a substantially circular cross-sectional area and a diameterof about 0.004 inches.

The distal end 64 of post 62 preferably is disposed at or near thedistal end of the spring coil 61. For example, the distal end 64 in oneembodiment terminates proximally of the guidewire tip (not illustrated),similarly to the embodiment illustrated in FIG. 1. Alternatively, thedistal end 64 is in contact with the guidewire tip, which can be moldedor machined integrally with the post 62 or secured thereto such as byknown biocompatible adhesives. In either embodiment, the distal end ofthe spring coil 61 is provided with any of the known atraumatic tipsconventional in the angioplasty arts, such as those formed by molding ordipping or brazing processes.

The post 62 can extend in a distal direction beyond the distal ends ofwire guides 72 and for a predetermined length. This can be one way ofcausing the steering region in operation to form an "elbow" bend, whichis believed clinically desirable. In addition, the portion of post 62disposed between the end of wire guide 72 and the guidewire tip canfunction as a safety wire for securing the guidewire tip against in vivodetachment.

By "elbow" bend, it is meant that the bend in the guidewire occurs at arelatively discrete position displaced proximally from the distal end ofthe guidewire. This enables a short length of floppy guidewire at thedistal end to facilitate negotiation of the artery with minimal traumato the vascular intima.

The length of the floppy tip beyond the more rigid steering region ofthe guidewire can be varied, depending upon a number of considerationswhich will be apparent to one of skill in the art, including thediameter of the vessels expected to be traversed. In one specificconstruction of the embodiment of FIGS. 7 and 11, for example, therelative dimensions are as follows. Length of each of guide 68 andanchor 72: about 0.010 inches. Axial distance between guide 68 andanchor 72: about 0.006 inches. Distance between end of anchor 72 anddistal tip of guidewire: about 0.140 inches. Diameter of control post62: about 0.004 inches. Diameter of spring wire of guidewire body: about0.002 inches. Outside diameter of assembled guidewire: about 0.014inches. In another specific embodiment, the length of the guides isabout 0.060 inches, the length of the anchors is about 0.010 inches, thegap between the guides and anchors is about 0.070 inches, and thedistance from the top of the guide to the distal end of the guidewire isabout 0.140 inches.

The post 62 extends in a proximal direction through the spring coil 61as far as may be desired for a given application, as will be understoodby one of skill in the art. For example, the central post 62 may extendproximally only as far as the proximal wire guide 68, or further in aproximal direction to impart greater rigidity to the spring coil 61 thanwould otherwise be present.

The post 62 should at some point along its length be secured againstaxial movement in the proximal direction relative to the spring coil 61.From a manufacturing standpoint, it has been found convenient to securethe proximal wire guides 68 both to the post 62 and to the interiorsurface of spring coil 61 for this purpose as will be discussed.However, the post 62 can also be secured to the coil 61 at otherlocations, such as at the proximal end of an axially elongated post 62.

A plurality of proximal wire guides 68 are provided, one for guidingeach of a plurality of deflection wires 70. Preferably, four proximalwire guides 68 are provided, equally spaced about the periphery of thecentral post 62. As will be apparent to one of skill in the art, threewire guides 68 spaced equidistant around the periphery of central post62 will also allow complete 360° steerability about the axis of theguidewire. However, the use of four deflection wires 70 is preferred.Similarly, the guidewire can be constructed having only two or even asingle deflection wire and proximal wire guide 68, with a commensuratereduction in the annular range of motion over which the guidewire may besteered.

A plurality of deflection wires 70 extend axially throughout the lengthof the spring coil 61, each through a unique proximal wire guide 68 tothe distal end 64 of post 62. Preferably, the distal end 64 of post 62is also provided with a plurality of distal wire guides 72, which canalso function as wire anchors, corresponding to each deflection wire 70.

In accordance with the preferred "post" embodiment of the presentinvention, four deflection wires 70 are utilized, each deflection wire70 having a unique proximal wire guide 68 and distal wire guide 72. Eachof the deflection wires 70 may be secured to the distal end of the postin any of a variety of manners, which will be apparent to one of skillin the art, such as by mechanical anchors, adhesives or thermal orchemical welding, or metal fastening techniques such as brazing orsoldering, depending upon construction materials.

Mechanical anchoring or welding of the distal end of deflection wire 70may be difficult to accomplish while providing sufficient strength toallow repeated steering maneuvers of the steering device 60 withoutseparation of the distal end of deflection wire 70 from the distal end64 of post 62. Thus, although the preferred embodiment is effectivelyprovided with four deflection wires 70, they are actually two continuousdeflection wires which loop across the distal end 64 of the post 62. Afirst deflection wire 70 extends distally through distal wire guide 72,continuously around or over the distal end 64 of central post 62 andback proximally through the opposing wire guide 72 and continuing ontowards the proximal end of the instrument. Alternatively, the distalends of the deflection wires are twisted or braided together, and extendas a safety wire up to the distal tip of the guidewire. In this manner,all four ends of the two continuous wires terminate at the proximal endof the guidewire where they connect to a control device permittingselective axial reciprocating motion thereof.

In accordance with one preferred embodiment of the present invention,proximal wire guide 68 is in the form of an elongate tubular body forreceiving the corresponding deflection wire 70 therethrough. The tubularwire guide 68 preferably is comprised of a material which can be readilyadhered to the central post 62, and preferably also can be adhered tothe adjacent loops of spring coil 61. Polyimide tubing, such as thatmanufactured by Polymicro Technologies, Inc. in Phoenix, Ariz., havingan axial length of approximately 0.010 inches and an inside diameter ofslightly greater than 0.0015 inches, preferably about 0.002 inches, hasbeen found particularly suitable for this purpose, and can be readilyadhered to a nylon post 62 using a suitable epoxy adhesive, such as thatmarketed under the name Ecobond by Emmerson Cuming of Canton, Mass. Inaccordance with another embodiment of the invention, the distal wireguide 72 is approximately 0.010 inches along and the proximal wire guide68 is about 0.030 inches long. Alternatively, metal tubing, such assolid wall tubing or wire wound tubing can be conveniently soldered orbrazed to a metal post.

The length of the tube is generally less important than the diameter,and the diameter must be sufficient that a deflection wire extendingtherethrough is capable of reciprocal motion with sufficiently lowfriction that steering may be accomplished. The wall thickness of thetube will directly affect the minimum diameter of the assembledsteerable guidewire, and is thus preferably minimized. For the polyimidetube disclosed above, the wall thickness is preferably as low as about0.0003 inches. As illustrated in FIG. 8, the proximal wire guide 68 isconveniently affixed to the spring coil 61 by applying an epoxy 69thereto.

Deflection wire 70 extends distally beyond the end of the proximal wireguide 68, and preferably through a distal wire guide 72. Deflection wire70 is a fine wire of a diameter sufficient to provide enough tensilestrength to allow steering of the guidewire without breaking, but smallenough to permit construction of guidewires suitable for angioplastyapplications Preferably, a stainless steel wire is used, and diametersas low as about 0.0015 inches have been found functionally sufficient.However, a variety of other metals or polymers may be used, and theminimum appropriate diameter for any given material can be readilydetermined by one of skill in the art.

Distal wire guide 72 is in the preferred embodiment a similarconstruction to proximal wire guide 68. Thus, distal wire guides 72 areformed by a plurality of elongate tubular guides adhered to the centralpost 62 for receiving the corresponding deflection wire 70 therethrough.Alternatively, the distal wire guide 72 can simply be a groove over thedistal end 64 of post 62, or a bore hole extending transversely throughthe center of central post 62.

Assembly of the steering device of the present invention may beaccomplished in a variety of ways which will be understood by one ofskill in the art, with many of the assembly steps being performed undermicroscopic vision. The proximal wire guide 68 and distal wire guide 72,when used, are preferably secured to the central post 62 by applying anadhesive thereto such as by dabbing with a 0.0015 inch diameter wire asan applicator. A first deflection wire 70 is threaded in a distaldirection through corresponding proximal wire guide 68, through distalwire guide 72, then back in a proximal direction through thecorresponding wire guides on the opposite side of post 62 and drawnthrough to the proximal end of the instrument. This assembly procedureis repeated for a second deflection wire. With the deflection wires 70in place, the entire distal end 64 of post 62 is dipped in or dabbedwith an epoxy or other biologically compatible material to form a cap 65to secure each of the deflection wires 70 against axial movementrelative to the control post 62. See FIG. 11.

The entire assembly of post 62 wire guides and deflection wires isthereafter inserted distal end first into the proximal end of a standardspring coil 61 and advanced until the proximal wire guide 68 isapproximately axially adjacent the beginning of the distal flexiblesteering region on the spring coil 61. An epoxy or other biocompatibleadhesive 69 is thereafter applied between the adjacent loops of springcoil 61 to secure the proximal wire guides 68 to the spring coil 61,thereby preventing axial movement of the post 62 relative to the springcoil 61. It has been found that polyimide tubing can be epoxied to theadjacent spring coil 61 using a 0.002 inch wire or other applicator tipunder microscopic vision. However, care must be taken that the epoxydoes not flow into contact with the deflection wire 70, in which casethe deflection wire 70 would be unable to slide axially within theproximal wire guide 68.

Referring to FIGS. 8-10, there is disclosed a further embodiment of thesteering device in accordance with the present invention. The steeringdevice 76 comprises a main body 77 having a proximal wire guide 80, awire anchor 84 and a pivot region 86. Preferably, the wire guide 80,pivot 86 and anchor 84 are integrally formed from a single extrusion ormolded part.

In accordance with a preferred embodiment of the invention, the mainbody 77 has a maximum diameter of as small as about 0.009 inches orsmaller, and is substantially circular in outer cross-sectionalconfiguration, except for a plurality of axially extending channels 85for receiving guidewires 88 therethrough. Each of the channels 85preferably has a depth of approximately 0.002 inches, so that0.0015-inch diameter stainless steel wire can slidably extendtherethrough. Channels 85 can conveniently be formed in the extrusionprocess as axial recesses of the type illustrated in FIGS. 8-10, or byproviding parallel sets of radially outwardly extending flanges whichextend axially to create a channel 85 therebetween.

Pivot 86 may be formed in any of a variety of ways, which will beapparent to one of skill in the art, and which will depend upon theconstruction material utilized. For example, in the case of athermoplastic polymeric extrusion, the pivot region 86 preferablycomprises a radially inwardly extending annular depression, which may beformed by application of heat and pressure or by stretching followingthe extrusion process. Alternatively, the pivot region 86 can beprovided by producing an annular recess through other operations such asby physically milling or cutting portions of the extrusion away, or,wire guide 80 and anchor 84 can be secured to a length of metal orpolymeric wire, spaced axially apart to provide a flexible length ofwire therebetween.

Preferably, the steering device 76 is provide with a deflection wire 88at each of the four 90° positions around the periphery thereof. (SeeFIG. 9.) As has been previously discussed, this can be accomplished byproviding four separate guidewires which are anchored at the distal endof the steering device 76. However, four deflection wires 88 areeffectively provided by assembling the steering device 76 with twocontinuous deflection wires 88, which loop over the distal end of wireanchor 84 and extend back in a proximal direction as has been discussed.

In assembling the embodiment of the steering device 76 illustrated inFIGS. 8-10, the deflection wires 88 are preferably crossed over thedistal end of an extruded main body 77, axially aligned with the freeends extending in the proximal direction. The distal end of the wireanchor 84 is thereafter dipped in or dabbed with an appropriateadhesive, such as an epoxy, to form a cap 90 for securing the deflectionwires 88 to the wire anchor 84.

A tubular sleeve 82, such as a length of heat-shrink tubing, isthereafter passed over the distal end of wire anchor 84 and advancedproximally into alignment with the proximal wire guide 80 in a mannerwhich captures each wire 88 within the respective channel 85. Uponapplication of heat, the annular sleeve 82 reduces in diameter to snuglyadhere to the proximal wire guide 80. It has been found that the use ofchannels 81, having a depth of approximately 0.002 inches, leaves asufficient tolerance after heat shrinking of sleeve 82 so that stainlesssteel wires having a diameter of approximately 0.0015 inches can freelyaxially move therethrough.

The steering assembly is thereafter inserted into a standard guidewirecoil 78, and advanced until the proximal wire guide 80 is approximatelyaligned with the proximal end of the flexible steering region of thecoil 78. The radial outside surface of the annular sleeve 82 maythereafter be secured to the adjacent coil loops of coil 78, such as bythe application of an epoxy or other adhesive 79, as has previously beendescribed.

As will be apparent to one of skill in the art, axial movement of anygiven deflection wire 88 in a proximal direction will cause the wire 88to slide through the channel 81 in proximal wire guide 80, and, becausethe wire 88 is immovably secured to the wire anchor 84, pivot region 86will flex to permit lateral displacement of wire anchor 84 in thedirection of the wire 88 which has been proximally displaced. In thismanner, as has been described, the steering device 76 permits selectivelateral displacement of the distal tip in any direction, and restorationof the position of the distal end of the steering device back into axialalignment with the axis of the adjacent portion of the guidewire orcatheter.

In a modified version (not illustrated) of the device illustrated inFIGS. 8-10, the pivot region 86 is deleted so that the assembled devicehas an anchor region 84 and a wire guide 80 axially spaced apart andsecured to the coils of guidewire body 78. Thus, no post appears in thisembodiment. In this embodiment, the deflection wires extend distallyfrom the wire guide 80 toward the anchor 84 as before, but instead ofextending substantially parallel to the axis of the steering device 76as illustrated in FIGS. 8 and 10, each deflection wire crosses the axisof the steering device to the opposite side thereof. Thus, for example,one deflection wire 70 extends through wire guide 80 at the 90°position, then distally at an incline relative to the axis of thesteering device to the 180° position on the anchor 84. The wire 70thereafter in the preferred embodiment loops around the distal end ofanchor 84 and extends proximally through the channel 85 at the 90°position thereof. Wire 70 thereafter extends diagonally across the axisof the steering device, through the wire guide 80 at the 180° position,and proximally to the steering control.

As a further alternative, the distal ends of the deflection wires (whichmay be the midpoint of a long, doubled back wire as previouslydiscussed) are brazed directly to the wire coils of the guidewire body.A brazed joint is most conveniently accomplished on the outside surfaceof the guidewire body, and the deflection wires preferably extendradially outwardly between adjacent loops on the guidewire body for thispurpose. In the case of two deflection wires formed from a single lengthof wire looping around the steering region of the guidewire, thedeflection wire is conveniently looped around the outside of theguidewire body to provide a site for brazing. When a brazed joint isused, the distal wire anchor 84 can be deleted.

Referring now to FIGS. 12 and 13, there is shown in FIG. 12 a partialsectional perspective view of a two-wire "ribbon" type steering device100 with the outer tubular casing removed. FIG. 13 shows a partialsectional perspective view of a another embodiment of a two-wiresteering device 120 according to the present invention. The tubularouter body 111 of the steering devices 100, 120 can be similar to thatof any of the various embodiments previously described.

In the steering devices 100, 120 shown, there is provided a flexiblesteering ribbon 110 disposed within the central lumen of the steeringregion 116 of the tubular outer body. As will be discussed, "flexible"can mean either a ribbon which can be physically bent or flexed in use,or a more rigid structure provided with a narrowing thereon or othertype of pivot to form a hinge. In this embodiment, rather than complete360° annular steerability about the axis of the guidewire, controlledsteerability within a single plane is achieved. One improvement over theprior art is that the steering region of the device, once controllablybent, can be restraightened by applying a positive traction to at leastone of the deflection wires.

The steering ribbon 110 may be molded, milled or extruded from any of avariety of known flexible materials, such as Nitinol, spring steel,nylon or other plastic materials. Preferably, the material will permitsufficient lateral flexibility while also exhibiting sufficient axialcompressive strength to optimize transfer of axial force into lateraldeflection. In another embodiment of the steering device 100, 120, thesteering ribbon 110 may be replaced by two or more substantiallyparallel ribbons or wires. Ribbon 110 can be brazed or otherwise secureddirectly to the body 111, or indirectly through proximal wire guides, asillustrated in FIG. 12.

The ribbon 110 is preferably made from a shape-memory Nitinol alloyhaving a transition temperature of less than about 20° C. Nitinol is athermal-memory nickel-titanium metal alloy that is flexible andcharacterized by a high tensile strength, as well as a high endurancelimit to stress fatigue. Nitinol has been found to be repeatedlydeformable without apparent loss of resiliency at the site ofdeformation.

The preferred Nitinol transition temperature for the invention describedherein is well below body temperature, such as 0° C. Those skilled inthe art will appreciate that the transition temperature of the Nitinolfamily of alloys can be manipulated over a relatively wide range byaltering the nickel-titanium ratio, by adding small amounts of otherelements, and by varying deformation and annealing processes. WhileNitinol alloys having a range of transition temperatures can be used,the transition temperature of the Nitinol alloy of this invention shouldbe sufficiently lower than the surrounding ambient temperature toprevent transition from occurring during use. Nitinol can be obtainedfrom Shape Memory Applications, Inc., Sunnyvale, Calif.

The steering ribbon 110, as shown, is preferably of substantiallyrectangular cross section but could also be of a variety of shapesincluding those that are substantially circular or ovoid. In general,any configuration which tends to promote the desired flexibility in asingle plane may be used, although a circular cross section structuremay also be used.

The narrower dimension of the approximately rectangular cross sectionillustrated in FIGS. 12 and 13 is preferably within the range of about0.0005 to about 0.003 inches. The low end of the range represents aboutas narrow a dimension as the inventors believe will be functional, giventhe known materials. The upper end of the range is only really limitedby the desired overall diameter of the instrument which, for example,may utilize a spring coil body having an inside diameter of 0.010 inchesand an outside diameter of 0.014 inches. In addition, increasing ribbonwidths will tend to require increased force to bend the ribbon.

Similarly, the long side of the rectangular cross section is limited atits maximum by the available inside diameter of the outer flexible coil.In accordance with one preferred embodiment, the cross-sectionaldimension of a rectangular ribbon for use in a guidewire is about0.001±50% by 0.007±50% inches. Preferably, the ribbon 110 hassubstantially the same cross-sectional area throughout its length,except in the region of a hinge in an embodiment such as thatillustrated in FIG. 13.

Flexibility across an arc of 180° or more in a single plane can also befacilitated by an appropriate pinching or narrowing of the ribbon 110.In the embodiment shown in FIG. 13, the hinge 175 is provided by anindentation 176 within the ribbon 110.

The hinge of FIG. 13 may be formed by molding, pinching, milling orstretching operations to form a narrowing having a greater propensity tobend than other portions of the ribbon 110. Preferably, the hinge isformed by pinching in a ribbon 110 having a rectangular cross section,however, any cross-sectional configuration may be used so long asflexibility in a single plane is encouraged and the ribbon 110 hassufficient rigidity and strength to withstand the forces applied inmultiple flexings and straightenings needed in steering the body 111.

In the embodiment shown by FIG. 12, the flexible hinge region 175 iseffectively provided by an axial space between tubular deflection wireguide 172 and anchor 168 which can be similar to the correspondingstructures described in connection with the embodiment illustrated inFIG. 7. Preferably, there is one guide 172 and one anchor 168 on eachside of the ribbon 110 for each of two deflection wires 170. The guides172 and anchors 168 function to position the wires 70 axially along thesteering ribbon as described in connection with FIG. 7 for securing thewires 70 to the steering post.

The exact length of the polyimide tubes preferably utilized as wireguides is not critical but the combined length of the tubing for guide172 and anchor 168 should typically be less than the overall ribbonlength. The length, diameter, construction and assembly of the guides172 and anchors 168 will be readily understood by one of skill in theart by reference to the drawings and description above and in connectionwith FIG. 7. In one embodiment, the wire guide 172 is about 0.030 inchesin length and the wire anchor 168 is about 0.010 inches in length.

The distance between the wire guide 172 and anchor 168 influences theability of the ribbon to deform in response to axial displacement of thedeflection wires. It is contemplated that a useful distance betweencoaxial wire guides and anchors is from about 0.010 to about 0.100inches, with a preferred distance of from about 0.020 to about 0.090inches, and a still more preferred distance of about 0.050 inches.Depending on the overall dimensions of the steering apparatus it isbelieved that a distance of up to 1 inch or more between guides 172 andanchors 168 is feasible. However, such an increase in distance betweenthe guides and anchors would create a longer hinge region requiringthicker ribbon dimensions to counter the tendency of the increasedlength to buckle, and to provide flexibility comparable to the preferredembodiment. In addition, excessive length between the wire guide andwire anchor will tend to result in too gradual an arc during steering tonegotiate relatively sharp arterial branches.

The ribbon of FIG. 12 can be coated with a substance to provideadditional support to regions of the ribbon proximal and distal to thehinge. This support layer or coating may be applied during manufacturein a co-extrusion process or, alternatively, the layer may be appliedfollowing or during ribbon manufacture as a dip or spray. Suitablecoatings or support layer material include but are not limited topolyimide, nylon or cyanoacrylate. The coating can be applied over theentire ribbon surface or the coating can be applied to the distal andproximal ends leaving the hinge region uncoated. If the support layer orcoating is applied over the entire ribbon surface, the coating over thehinge region can be subsequently removed in at least one location byscraping, grinding, cutting, melting or by laser. By providing the axialspace 175 between guide 172 and anchor 168 that is at least partiallyuncoated, greater flexibility in the hinge region is achieved ascompared with the proximal or distal sections of the ribbon.

The coating can be applied in a uniform thickness or it can be appliednon-uniformly. The thickness of the coating is determined by the methodof application as well as by physical constraints imparted by thedimensions of the apparatus. For example, the final width of the ribbontogether with the tubing and deflecting wires need be less than thefunctional inner diameter of the flexible housing thus providing a limitto the coating thickness. The coating can be applied so that it isthicker on the proximal portion of the ribbon relative to the distalportion thereby minimizing ribbon movement relative to the housing atthe proximal portion yet permitting movement of the ribbon relative tothe housing at the distal portion of the ribbon. Conveniently, thecoating can also function as the adhesive to secure the wire guides andwire anchors to the ribbon.

In the preferred embodiment, the deflection wires 170 are formed as amulti-filament complex. Alternatively, each deflection wire couldconsist of a single wire filament. The multi-wire filaments of thepreferred embodiment are twisted or braided together to give about thesame strength as a wire monofilament of the same overall diameter yetthe multi-filament nature provides added flexibility. A range of fromabout 3-10 monofilament strands that are braided or entwined togetherare contemplated. Preferably, 7 strands of type 304 stainless steel eachwith a diameter of about 0.0005 inches are braided to provide an overalldiameter of about 0.0015 inches. The seven strand multi-filament wireprovides tensile strength on the order of 400,000-450,000 psi and isroughly equal in diameter to the single strand deflection wirepreviously described. Suitable wire strands can be obtained from FortWayne Metals Research Products Corp., Fort Wayne, Ind.

The multi-filament bundle or single strand deflection wire could have anoverall diameter in the range 0.001 to 0.005 inches. The choice of finalwire diameter is limited by the internal diameter of the wire housingthat contains the ribbon, polyimide tubing and deflection wire as wellas by the tensile strength required to translate an applied axial forceinto lateral deflection.

A lubricous coating is preferably applied to the surface of thedeflection wire in order to facilitate smooth motion of the wire in thehousing. Any of polyimide, silicone, polytetrafluoroethylene or nyloncan be applied to the surface of the wires to facilitate smooth movementof the wire along the proximal end of the steering ribbon. In apreferred embodiment, polytetrafluoroethylene coated deflection wire isemployed to permit even, continuous movement in response to an appliedsteering force. The wire can be coated by spray, dip, or other meansknown to one of skill in the art.

As discussed in connection with previous embodiments, at least onedeflection wire 170 s secured with respect to the ribbon 110. In apreferred embodiment, there are two deflection wires 170, one on each oftwo opposing sides of the ribbon 110 with the distal most portions ofthe deflection wires (which may be the midpoint of a continuous, doubledback wire as previously discussed) secured with respect to the steeringribbon 110. Securing may be done by brazing, gluing, welding orsoldering the wire directly to the top of the steering ribbon.

The deflection wires alternatively continue distally of the ribbon andmeet at a centrally fixed location where they are twisted or coiledtogether. This joint may be additionally strengthened and affixed bysoldering, brazing, or gluing the wires to the distal end of the ribbon110. One or both of the wires preferably continues distally and isaffixed to the catheter tip such as by soldering or brazing to provide asafety wire.

Torque is readily transmitted from the proximal control to the distalsteering apparatus by either the use of hypodermic needle tubing or bytri-plex spring supplied by Microspring Company, Inc., Nowell, Mass.Like the deflection wire, the tri-plex spring guidewire could also becoated with a biocompatible lubricous coating. Such a coating couldreduce friction between the guidewire and the vessel wall. Tri-plexspring provides the guidewire housing with sufficient rigidity such thatforce applied at the proximal end of the device is efficientlytransferred to the distal steering ribbon.

The tri-plex spring should be closely coiled over the majority of theapparatus and preferably at least about 7/8 of the overall length of thedevice. The distal end of the apparatus is comprised of a small regionof loose coiling that is bounded on either side by coiling having arigidity that is greater than the loose coiling but less rigid than thetri-plex spring. Thus, the majority of the apparatus is formed from thetri-plex spring with the distal region, preferably one eight or less ofthe total length, made of coiling of intermediate rigidity, followed byflexible coiling and ending in coiling of intermediate rigidity. Thesteering ribbon is positioned at or near the proximal junction of theintermediate coiling and the looser coiling. Thus proximally appliedforce is translated to the steering ribbon and the looser coil withinthe steering region deflects laterally in response to ribbon deflectionthereby providing a steering direction.

In use, the steering device 100 or 120 can be steered in either of twodirectly opposite steering directions by displacing one of thedeflection wires 170. By axial displacement of either of the twodeflection wires, a range of motion of the tip of the device is achievedalong a semicircular arc within a plane lying on the longitudinal axisof the steering device 100, 120.

After the device is introduced into the vasculature or other branchedsystem, and a branch or a turn is encountered, in order to enter thebranch or turn, the device can be rotated (torqued) to align one of thetwo steering directions with the branch or turn to be entered. Thedevice can be steered by axial displacement of one of the deflectionwires. Advantageously, after the device has been steered toward onedirection, the device can be easily straightened to some degree bydisplacing the deflection wire opposing the side toward which the devicewas steered. The device can then be further advanced through thevasculature.

Referring to FIGS. 14-23, there is disclosed a steerable guide wire 180in accordance with a further embodiment of the present invention.Although disclosed in the context of a guidewire embodiment, thesteering and torque transmission aspects of this embodiment of thepresent invention can be used in a variety of other implements, such asin a steerable balloon catheter or "balloon on a wire" design. Guidewire 180 generally comprises an elongate tubular body portion 182, and adistal tip 184. Steering region 186 is disposed within about 2 cm, andpreferably within about 1 cm of the distal tip 184.

The body of steerable guide wire 180 may be any desired length frominches to many feet depending upon the intended application. In atypical angioplasty guide wire or catheter, the body will typically beseveral feet long, and preferably will be within the range from about135 cm to 175 cm, as is typical of existing angioplasty catheters andguide wires, respectively. Guide wires are typically somewhat longerthan the corresponding catheter to facilitate catheter insertion andexchange as is well known in the art.

The proximal portion 181 of the tubular body 182 typically compriseshypodermic needle tubing, although other materials such as a spring coilor polymeric tube are also known for this purpose. The distal portion ofthe tubular body preferably comprises a metal coil. The proximalhypotube section is typically about 155 cm in length, and the distalmetal coil section is typically about 30 cm in length. To facilitatevisualization, either the distal most 2 cm or so of the spring coil, orthe entire 30 cm of spring coil comprises platinum or other radiopaquematerial.

Preferably, the hypotube section 181 of the main body 182 in a guidewireor balloon on a wire embodiment for coronary vascular applications hasan outside diameter of from about 0.013 to about 0.018 inches and aninside diameter of within the range of from about 0.008 to about 0.009inches or larger. Preferably, the inside diameter is approximately0.0085 inches. For peripheral vascular applications, the hypotubesection 181 will typically have an external diameter on the order offrom about 0.035 to about 0.040 inches. Suitable hypodermic needle stockis available from a variety of sources, such as the 304 stainless steelhypodermic stock available from MicroGroup, Inc., Medway, Mass., Popperand Sons Corp., New Hyde Park, N.Y., or Uniform Tubes, Inc.,Collegeville, Pa.

The proximal hypodermic needle stock section 181 and distal wire coilsection 183 are merged at a transition section 187. Referring to FIG.19, the transition from the hypodermic needle stock 181 to the springcoil 183 is preferably accomplished with a minimal or no change ineither the inside diameter or the outside diameter of the body 182. Inthe illustrated embodiment, the distal end 185 of the hypodermic tubesection 181 is provided with a helical channel such as by a wireelectrical discharge machine (EDM) utilizing techniques which are knownin the art. In general, the hypotube is fixtured in a servomotorcontrolled rotary indexer which accurately rotates the tube while theentire fixture is advanced at a controlled rate. The EDM machine isstationary and the wire is advanced into the hypotube wall to cut thespiral as the tube rotates and advances. See, for example, FIG. 22,illustrating the helical channel cut into the distal end 185 of thehypotube segment.

Referring to FIG. 22, there is disclosed a helical channel having achannel width within the range of from about 0.0025 to about 0.0030inches. The channel defines a helical ribbon having a width within therange of from about 0.0080 to about 0.0090 inches. The hypotube in theillustrated embodiment has an outside diameter of about 0.013 inches,and the helical channel was cut into the distal portion of a hypotubesegment having an axial length of about 150.5 cm. Preferably, thehypotube is provided with at least 3 or 4 complete threads.

The proximal most windings of the coil 183 are threaded onto the helicalchannel, to provide a transition 187 having a mechanical interfitbetween the two adjacent sections. The transition 187 is strengthened byflowing solder or other suitable bonding material into the helicalchannels with the coil installed. Thereafter, the exterior may bepolished to a smooth surface. However, any of a variety of otherjunctions between solid tubing stock and spring coil stock may beutilized, as may be known to or devised by persons skilled in the art.

The metal coil section 183 may be constructed in any of a variety ofways known in the art, such as by tightly winding a coil of a hightensile strength wire of a resilient, noncorrosive metal such asstainless steel or platinum. Typical wire for this purpose will have acircular cross-section with a diameter of from about 0.001 to about0.005 inches. Alternatively, the wire may have a rectangularcross-section of from about 0.001 to about 0.020 inches by from about0.001 to about 0.040 inches, or other variations known in the art. Morepreferably, the rectangular wire embodiment has cross sectionaldimensions of from about 0.001 to about 0.004 by from about 0.004 toabout 0.010 inches. The preferred coil for use in the present embodimentis a tightly wound stainless steel or platinum wire having a diameter ofabout 0.0025, to produce a coil having inside diameter of about 0.0085inches and an outside diameter of about 0.0135 inches.

The distal portion of the metal coil section 183 comprises a steeringregion 186. See FIGS. 15 and 16. Preferably, the windings of the springcoil 183 distal to the wire guide 200 are separated slightly, toincrease the relative flexibility of the steering region 186. "Loosely"wound coil sections may be produced in accordance with a variety oftechniques well known in the art.

The steerability function of the guidewire in accordance with thepresent invention is optimized if the adjacent windings of spring coil183 are "tightly wound" or in contact with each other proximally to wireguide 200. This resists axial compression and enables the wire guide 200to function as the steering "platform" as has been described in previousembodiments. In this manner, and in view of the additional function ofwire guide 200 of providing an axial anchor for steering ribbon 202,proximal motion of pull wire 188 produces a lateral component of forceas the effective length of the pull wire segment between guide wire 200and junction 206 is reduced compared to the fixed axial length of thesteering ribbon 202 between wire guide 200 and junction 206.

That portion of the steering element between its point of attachmentwith respect to the coil 183 and its point of attachment to the pullwire thus functions in the same manner as the "post" and "ribbon"described in connection with previously described embodiments. Althoughthe post in this embodiment is secured against axial movement by beingsecured to the wire guide 200, other means of attachment can be utilizedto practice the present invention. For example, plate 50 illustrated inFIG. 4 or other structure which can be inserted between adjacentwindings can be used. Alternatively, the steering ribbon 202 can bebonded directly to the interior of spring coil 183.

In view of the foregoing description of the steering mechanism of thepresent embodiment, which will be described in greater detail twoadvantages of the designs disclosed herein can be seen. Initially, thelength of the guidewire disposed between the "platform" formed in thisembodiment by wire guide 200 secured to the spring coil 183 and thejunction 206 directly affect the radius of the bend produced in theguidewire by axial displacement of pull wire 188.

For example, in an embodiment having an outer diameter of 0.014 and adistance from wire guide 200 to distal junction 206 of 0.100, the radiusof the turn when bent to about a 90° angle is about 0.06. In general,desirable radii in a percutaneous coronary transluminal angioplastyapplication will be within the range of from about 0.020 to 0.180.However, individual cardiologists may develop a preference for a wirehaving a particular radius of curvature, which may be within or outsideof the above recited range. In general, increasing the distance betweenthe wire guide 200 and the distal junction 206 will enlarge the radiusof curvature while decreasing the distance between the wire guide 200and the distal junction 206 will reduce the radius of curvature. Theprecise distance required to produce a given radius can be readilydetermined through routine experimentation by one of skill in the art.

A second advantage of the designs disclosed herein is that the distancefrom the center of the bend to the distal tip 184 of the guidewire 180can also be varied as desired. For example, in the embodimentillustrated herein, the distal junction 206 is displace proximally fromthe distal tip 184 of the steerable guidewire 180 by approximately 2 mm.This produces a "dogleg" bend, which, as previously described, ispreferred by many cardiologist. By varying the relative location of thesteering region 186 within the guidewire 180, the relative dimensions ofthe dogleg bend can be varied as will be appreciated by one of skill inthe art.

Extending axially through the central lumen of the steerable guide wire180 is a first pull wire segment 188. First pull wire segment 188preferably comprises a solid wire made from a metal or polymer havinggood axial compressive strength and torque transmission characteristics.In the illustrated embodiment, first pull wire segment 188 comprises astainless steel wire having a proximal portion 188a of circularcross-section, having a diameter of approximately 0.0075 inches. Theouter diameter of pull wire 188 and inside diameter of hypotube section181 may be varied within a relatively wide range as will be understoodby one of skill in the art, as long as the pull wire segment 188 remainsaxially movable within hypotube section 181 without excess friction.

Transmission of torque along the length of the guidewire 180 isoptimized by inclusion of an optional torque transmitter 189 between thepull wire 188 and hypotube section 181. Referring to FIGS. 19 and 20,torque transmitter 189 comprises a flat 192 provided on the surface ofpull wire 188 such as by milling or grinding. The flat 192 cooperateswith a corresponding torque surface 194 on the hypotube 181. Torquesurface 194 is preferably provided by crimping the hypotube to produce aflat or irregular wall section thereon.

The axial length of the flat 192 is preferably within the range fromabout 0.2 cm to about 0.5 cm, thereby producing a proximal shoulder 193and a distal shoulder 195. The separation of the proximal shoulder 193and distal shoulder 195 can, if desired, be utilized to limit the axialrange of motion of the pull wire 188 within tubular body 182 as will beapparent to one of skill in the art. In general, the axial range oftravel of the pull wire 188 within the guidewire body is about 0.200inches or less for normal steerability. The depth of the flat 192 canvary considerably, but, in a preferred embodiment, is within the rangeof from about 0.0045 to about 0.0055 inches.

Alternatively, the flat section 192 can extend the entire length offirst pull wire segment 188, or first pull wire segment 188 can comprisea rectangular wire throughout or other cross-sectional configurationsusceptical to rotational interlocking such as by a torque surface 194.Preferably, however, at least the portion of the pull wire 188 thatextends within the spring coil 183 is circular in cross section tominimize whipping.

In the illustrated embodiment, portion 188a of first pull wire segment188 extends distally from a circular cross section of about 0.0075inches at the torque transmitter 189 through one or a series oftransition zones, to a reduced cross-sectional rectangular dimension ofabout 0.001 inches by about 0.003 inches at 188e. See FIG. 23. The crosssectional area reduction (continuous taper or steps) can extend over anyof a variety of axial lengths, as will be apparent to one of skill inthe art. The rate of taper has been found to affect the relativeflexibility of the tip, and the present inventors prefer the taper tooccur over an axial length of about 12 cm. Tapering can be smooth orstepped, and can be accomplished in any of a variety of manners, such asby grinding in a centerless grinder or an O.D. grinder. Flattening ofdistal portion 188e is then accomplished by compression between adjacentrollers or other technique depending upon the construction material.

In the preferred embodiment, the cross sectional dimension of the pullwire 188 is reduced in the distal direction over a series of steps asillustrated in FIG. 23. Proximal portion 188a, in a preferred coronaryartery embodiment, has a diameter of approximately 0.0075 inches. Atabout 13 cm from the distal end of segment 188e, a transition 188breduces the diameter to 0.0060 inches at 188c. The axial length of thetransition 188b is approximately 3.5 cm. The axial length of segment188c is about 6.0 cm.

Thereafter, at about 3.5 cm from the distal end of section 188e,transition 188d begins. Transition 188d provides a taper over an axiallength of about 3 cm to a segment 188e having a diameter ofapproximately 0.0025 inches. Prior to assembly of the steerableguidewire 180, the segment 188e is flattened between adjacent rollers toproduce a rectangular ribbon having a thickness of about 0.0010 inches.The length of section 188e is thereafter trimmed to approximately 5 mm.

Referring to FIG. 18, a second torque transmitter 192 is disposed withinthe coil 183 distally of transition 188d for axially slidably receivingflattened region 188e of the first pull wire segment 188. Torquetransmitter 192 preferably comprises a structure affixed to the interiorwall of coil 183, having a configuration to rotationally engage theflattened region 188e of first pull wire segment 188. Preferably, torquetransmitter 192 comprises a length of tubing which has been molded orcompressed into a generally oval cross-sectional configuration forreceiving flattened region 188e.

For this purpose, stainless steel hypotube stock having a 0.004 inchinside diameter and 0.007 inch outside diameter, and cut to a length ofapproximately 0.030 inches, is flattened in a die having stops toprevent complete collapse as will be understood by one of skill in theart. The resulting oval mini hypotube may be soldered to the adjacentwindings of coil 183, to rotationally link the coil 183 with theflattened region 188e of first pull wire segment 188. Additionalvariations on torque transmitter 192 will be apparent to one of skill inthe art in view of the present disclosure.

First pull wire segment 188e is connected to a second pull wire segment198 at junction 196. Preferably, junction 196 comprises a length ofoverlap of the first pull wire segment 188e and second pull wire segment198, which are connected such as by soldering. Although the foregoingdesign is preferred by the present inventors, the main pull wire 188 canalternatively extend throughout the length of the guidewire, without anyjoints or discontinuities.

Second pull wire segment 198 preferably comprises a flexible pull wiresuch as a multifilament stranded wire having an outside diameter ofabout 0.002 inches. Second pull wire segment 198 preferably extends allthe way from junction 196 to the distal tip 184 where it is linked tothe coil 183 and or tip 184 such as by soldering. That portion ofsegment 198 which extends between junction 206 and tip 184 functions asa safety wire.

In a multifilament embodiment, a range of from about 3 to about 10monofilament strands are braided or entwined together to produce thesecond pull wire segment 198. Due to braiding geometry, 3 or 7 strandsare generally used. Preferably, seven strands of type 304 stainlesssteel each having a diameter of about 0.0007 inches are braided toprovide a pull wire having an overall diameter of about 0.002 inches ashas been previously discussed.

Second pull wire segment 198 extends distally from junction 196 througha wire guide 200. Wire guide 200 preferably comprises a tubular bodywhich is secured to both the windings of the coil 183 and to thesteering ribbon 202. Preferably, the wire guide 200 has an insidediameter of about 0.0025 inches and an outside diameter of about 0.0035inches, made from wire having a diameter of about 0.0005 inches.Suitable tubular wire guides can be produced by winding fine wire abouta wire mandrel to produce a small coil. Stainless steel wire having adiameter of about 0.0023 inches has been found preferable for thispurpose.

The wire guide 200 is preferably soldered to adjacent loops of wire coil183. Although a variety of methods are known in the art for securingcomponents of guide wires together, such as adhesives, thermal bonding,solvent bonding, brazing and the like, solder has been preferred by thepresent inventors. Thus, all of the components of the guide wiredisclosed in this embodiment are preferably stainless steel or othersolderable metal. Soldering, which can be conducted in the area of about500° Fahrenheit is preferred over brazing, which requires highertemperatures in the neighborhood of about 1200° Fahrenheit. Brazingtemperatures have appeared to the present inventors to induce fatigueand increase the likelihood of failure in the finished product.

Preferably, the wire guide 200 has an axial length of about 0.030inches, although any of a variety of axial lengths can be utilized aswill be apparent to one of skill in the art.

Steering ribbon 202 extends distally from wire guide 200 for about 0.1inches, where it is affixed such as by soldering to the second pull wiresegment 198 at distal junction 206. Steering ribbon 202 preferably alsoextends proximally from the wire guide 200 to regulate the flexibilityof the steerable guide wire 180. In the illustrated embodiment, steeringribbon 202 extends proximally for a distance slightly in excess of about2 cm. Approximately midway between the wire guide 200 and the proximalend of steering ribbon 202 is a transition 208 at which the outsidedimensions of the steering ribbon are reduced from about 0.001 by 0.003inches on the proximal side of transition 208 to about 0.0004 by 0.008inches on the distal side of transition 208.

The wire guide 200 can be conveniently secured within coil 183 byseparating the adjacent loops slightly and soldering the coil 183directly to the wire guide coil 200. Alternatively, a spacer 201 formedfrom a second coil or wire can be adhered to the opposing side ofsteering ribbon 202 to provide additional bonding strength. Spacer 201is similarly soldered or otherwise secured both to the interior ofadjacent windings on coil 183 and to steering ribbon 202.

In one particular embodiment of a guide wire incorporating this aspectof the present invention, the distance from the distal tip 184 to thedistal end of junction 206 was 2.3 mm. The length of junction 206 wasapproximately 0.015 inches. The distance from the proximal end ofjunction 206 to the distal end of wire guide 200 was approximately 0.100inches. The axial length of wire guide 200 was about 0.030 inches. Thus,the distance from the distal tip 184 to the distal end of wire guide 200was approximately 5.25 mm.

The distance from distal tip 184 to the transition 208 on steeringribbon 202 was approximately 13.30 mm. Transition section 208 wasdisposed approximately 1 mm to the distal side of the distal end ofjunction 196. The junction 196 comprised an overlap of flattened region194 on first pull wire segment 188 and second pull wire segment 198 ofapproximately 2 mm. The overall distance from the distal end of torquetransmitter 189 to the distal tip 184 was approximately 20.00 mm.

The foregoing dimensions may be varied considerably, depending on theintended use of steering devices incorporating the present invention, aswill be readily understood by one of skill in the art.

It must be pointed out that the devices of the present invention canreadily be modified by one of skill in the art to allow lateraldisplacement in only a single direction instead of two opposingdirections. For example, the groove in a living hinge type device can beprovided on only a single side of the steering ribbon, or other meansfor stopping or resisting flexing in one direction can be employed aswill be readily apparent to one of skill in the art.

An advantage of the simplified steering devices 100, 120 of the presentinvention is that they can be operated in a manner similar to thatemployed on conventional steering devices for coronary angioplasty andother medical procedures. Thus, one skilled in the art of the prior artprocedures could learn to manipulate the steering device of the presentinvention with little or no additional training.

Although this invention has been described in terms of certain preferredembodiments, other embodiments that are apparent to those of ordinaryskill in the art are also within the scope of this invention.Accordingly, the scope of the invention is intended to be defined onlyby reference to the appended claims.

We claim:
 1. A steerable device for percutaneous transluminal insertioninto the coronary or peripheral vascular system and controllednegotiation of branches and turns therein, said device comprising:anelongate support structure having a proximal and a distal end fortransmitting axial force from the proximal end of the support structureto the distal end thereof; a steering element extending distally fromthe distal end of the support structure; a fulcrum at the intersectionof the support structure and the steering element; and a core wireextending generally parallel to the support structure and secured to thesteering element at a point of attachment which is distal from thefulcrum; wherein axial movement of the core wire in a proximal directionrelative to the support structure causes a lateral deflecting of thesteering element distally of the fulcrum.
 2. A steerable device as inclaim 1, wherein at least a portion of the support structure comprisessolid walled tubing.
 3. A steerable device as in claim 1, wherein atleast a portion of the support structure comprises a spring coil.
 4. Asteerable device as in claim 3, wherein adjacent loops of the springcoil are normally in contact with each other.
 5. A steerable device asin claim 1, wherein the core wire is rotationally linked to the supportstructure by at least one torque transmitter.
 6. A steerable device asin claim 5, comprising at least two torque transmitters.
 7. A steerabledevice as in claim 1, further comprising a spring coil surrounding thesteering element.
 8. A steerable device as in claim 1, wherein thefulcrum is disposed within about 10 mm from the distal end of thesteerable device.
 9. A steerable device as in claim 8, wherein thefulcrum is disposed within about 6 mm from the distal end of thesteerable device.
 10. A steerable device as in claim 1, wherein thesupport structure comprises an elongate tubular body, the steeringelement is axially immovably secured to the distal end of the supportstructure, and is relatively laterally flexible compared to the supportstructure so that proximal axial displacement of the core wirepreferentially causes the steering element to bend laterally.
 11. Asteerable device as in claim 10, wherein the tubular body extendsdistally beyond the fulcrum to enclose the steering element.
 12. Asteerable device as in claim 1, wherein the fulcrum comprises a solderjoint between the support structure and the steering element.
 13. Asteerable device as in claim 1, wherein the fulcrum comprises atransition between a proximal portion of the support structure which isrelatively laterally inflexible, and a distal steering element portionwhich is relatively laterally flexible.
 14. A steerable device as inclaim 1, wherein the fulcrum comprises a transition between a proximalportion of the support structure which is relatively axiallynoncompressible and a distal steering element portion which isrelatively laterally flexible.